This invention relates generally to low softening, low thermal expansion coefficient seal glasses and more particularly to a process for preparing a copper oxide containing glass useful in forming gas tight glass seals and the glass compositions prepared thereby.
Low softening point, low thermal expansion coefficient copper containing glass compositions are useful in sealing various surfaces such as ceramics, metals, and glasses and for joining such surfaces together. Such copper glasses are used, for example, to seal together the glass substrates used to form gas display panels in which a gas is contained in a space between electrode bearing glass substrates. The gas is ionized by applying a potential to various electrode segments in order to form visible alphanumeric characters.
One problem associated with the formation of such seals from copper oxide glasses is the conversion of CuO to Cu.sub.2 O during preparation of the glass compositions. The resulting Cu.sub.2 O crystals are believed to be responsible for causing the seals to be porous rather than gas tight as required. The crystals may also form seeds or bumps on rods which are drawn from the glass for use in seal formation. These bumps sometimes break from the rod and contaminate the inside of the panel.
The process of the invention permits the formation of a copper seal glass in which the cuprous oxide crystal content is controlled so as to permit clean, gas tight seals to be formed.